Generation and measurement of isolated attosecond pulses with enhanced flux using a two colour synthesized laser field.

We have generated isolated attosecond pulses and performed attosecond streaking measurements using a two-colour synthesized laser field consisting of a strong near-infrared few-cycle pulse and a weaker multi-cycle pulse centred at 400 nm. An actively stabilized interferometer was used to coherently combine the two pulses. Using attosecond streaking we characterised the electric fields of the two pulses and accurately retrieved the spectrum of the multi-cycle pulse. We demonstrated a two-fold increase in the flux of isolated attosecond pulses produced and show that their duration was minimally affected by the presence of the weaker field due to spectral filtering by a multilayer mirror.

Dental Care-Related Fear and Anxiety: Distress Tolerance as a Possible Mechanism.

Distress tolerance, the degree to which one is able to cope with and endure negative emotional states, has been broadly applied to understand and treat a variety of health (including behavioral) problems, but little is known about its role in oral health care and specifically dental care-related fear and anxiety, making it a novel construct in the oral health care literature. This cross-sectional study examined distress tolerance as a possible predictor of dental fear and anxiety among a sample of adults with and without diagnoses of dental phobia, investigated possible differences in levels of distress tolerance between adults with and without dental phobia, and determined possible associations between distress tolerance and fear of pain, anxiety sensitivity, and depression. Using 52 volunteers (n = 31, dental phobia group; n = 21, healthy comparison group), this investigation used self-report measures of distress tolerance, fear of pain, anxiety sensitivity, dental fear, and depression. The Anxiety Disorders Interview Schedule, a semi-structured interview, was used to assess for dental phobia and other psychological disorders. Distress tolerance significantly predicted dental fear and anxiety, even after controlling for age, sex, fear of pain, anxiety sensitivity, and depression. In addition, the dental phobia group had lower distress tolerance than the healthy comparison group. Distress tolerance was significantly associated with fear of pain, anxiety sensitivity, and depression. Findings indicate that low distress tolerance plays a unique and distinct role as a possible mechanism in the genesis of dental care-related fear and anxiety and phobia and may exacerbate the experience of other states, including fear of pain and anxiety sensitivity. Knowledge Transfer Statement: Results indicate that patients who have a lower ability to tolerate emotional and physical distress may have higher levels of dental care-related fear and anxiety and even dental phobia, as well as associated sequelae (e.g., avoidance of dental care). Treatment of highly fearful dental patients may helpfully include a focus on increasing distress tolerance.

Recall of Dental Pain and Anxiety in a Cohort of Oral Surgery Patients.

Dental patients generally recall more pain than they originally report, with ratings of pain related to state anxiety and dental fear, but the role of depression in recall of dental pain remains uncertain. This study examined the relative contributions of different variables in explaining dental pain recalled after tooth extraction. Patients presenting for tooth extraction, prior to extraction, rated their current dental pain and state anxiety, prediction of pain and state anxiety during extraction, depression, and dental fear. Immediately postprocedure and then 1 mo later, patients rated their pain and state anxiety during extraction. Hierarchical linear regression equations were used to explain variance in recalled pain and state anxiety. In addition, patients were divided into high and low dental fear and depression groups and compared on ratings of pain and state anxiety across time. In a final sample of 157 patients, the most important predictors of recalled pain were pain reported during extraction (ß = .53) and recalled state anxiety (ß = .52). Dental fear and depression had a significant interaction: only when patients reported less depression did those patients who reported more dental fear also report more pain than patients who reported less dental fear (P < 0.05, ω(2) = .07). Patients who reported more depression entered the dental operatory reporting more pain, but all patients generally reported less pain during extraction than they predicted or recalled. Memory of state anxiety and pain reported during tooth extraction, not depression or state anxiety at the time of extraction, were critical factors in memory of the pain associated with the procedure. At higher levels of depression, patients higher and lower in dental fear did not differ in report of pain. Future studies are needed to further clarify interactions of depression and dental fear over time.

2 × 2 Tables: a note on Campbell's recommendation.

For 2 × 2 tables, Egon Pearson's N - 1 chi-squared statistic is theoretically more sound than Karl Pearson's chi-squared statistic, and provides more accurate p values. Moreover, Egon Pearson's N - 1 chi-squared statistic is equal to the Mantel-Haenszel chi-squared statistic for a single 2 × 2 table, and as such, is often available in statistical software packages like SPSS, SAS, Stata, or R, which facilitates compliance with Ian Campbell's recommendations.

The influences of psychotic symptoms on the activities of daily living of individuals with Alzheimer disease: a longitudinal analysis.

OBJECTIVES: Psychotic symptoms associated with Alzheimer Disease (AD) contribute to excess functional dependence. Longitudinal studies have generally examined the association between rates of functional decline and the occurrence of psychotic symptoms from either a single evaluation or from multiple evaluations rather than through changes in frequency and severity of symptoms. Although the presence or absence of psychotic symptoms at initial or follow-up examinations may be associated with changes in functional status, the nature of the relationship between changes in these domains cannot be inferred. We examine the association between changes in the frequency of psychotic symptoms and changes in dependence in activities of daily living (ADL) over a period ranging from 1 to 74 months (median = 17.7). METHOD: Data from a cohort of 234 individuals referred to a memory clinic were analyzed using multilevel linear regression. Information on ADL, behavioral and psychological symptoms, depression, and cognition was collected. RESULTS: An increase in the frequency of psychotic symptoms had a unique influence on the deterioration of basic ADL, after controlling for demographic variables, changes in cognition, depression, and other behavioral and psychological symptoms (B = -.017, p = .003). However, changes in psychotic symptoms did not significantly contribute to declines in the ability to perform instrumental ADL (B = -.008, p = .439). CONCLUSION: Changes in psychotic symptoms may influence basic but not instrumental ADL over time. These findings may have ramifications for studies and treatment plans for individuals with AD who demonstrate psychotic symptoms.

Low-level persistence of human papillomavirus 16 DNA in a cohort of closely followed adolescent women.

Most human papillomavirus (HPV) infections in young women become undetectable by standard assays after a few months. It is possible that many HPV infections do not actually clear, but persist at very low levels for years, becoming detected again later in life. The purpose of this study is to describe HPV 16 clearance, reappearance, and low-level persistence in a cohort of adolescent women. Adolescent women (N = 66), not vaccinated against HPV, were recruited from 1998 to 2008 into a longitudinal study. Self-collected vaginal samples were obtained quarterly and tested for HPV by Linear Array HPV Genotyping Test (LA-HPV). To explore low-level persistence, a type-specific nested PCR for HPV 16 (TSN-PCR-16) was developed. Women with HPV 16 detected by LA-HPV had their negative swabs retested with TSN-PCR-16. Forty-two participants with HPV 16, followed for a mean of 6.3 years, were analyzed. Using LA-HPV, the median duration of HPV 16 detection was 428 days (SD 852.5 days). TSN-PCR-16 detected HPV 16 during periods of LA-HPV non-detection in samples from many women. Using a combination of LA-HPV and TSN-PCR-16 results, the median duration of HPV 16 detection was 1,022.5 days (SD 943.7 days). The durations of detection differed significantly between the two methods (P = 0.0042) with a mean difference of 434.5 days. In adolescent females, duration of HPV 16 detection was significantly longer when TSN-PCR-16 was combined with LA-HPV. Some apparently cleared HPV 16 could be shown to persist at low levels using nested PCR.

Memory of pain and anxiety associated with tooth extraction.

Concerns regarding pain constitute a large component of dental anxiety, and patients with high dental anxiety are likely to have exaggerated memory and prediction of dental pain. It remains to be investigated, however, if memory of anxiety is exaggerated in a manner similar to that of pain, and if anxiety and pain assimilate in memory over time. A sample of 79 patients presenting for emergency extraction rated their anxiety and pain before, during, and two weeks after the procedure. Measures of trait dental anxiety and fear of pain also were collected. All patients exaggerated their recall of procedure pain, but only those high in trait dental anxiety exaggerated their recall of anxiety. Highly anxious patients reported more pain prior to the procedure and expected more pain; ratings of anxiety and pain for all participants assimilated over time.

Human papillomavirus detection and typing in thin prep cervical cytologic specimens comparing the Digene Hybrid Capture II Assay, the Roche Linear Array HPV Genotyping Assay, and the Kurabo GeneSquare Microarray Assay.

Three methods for the detection of HPV DNA were compared in cervical cytologic specimens: the Digene Hybrid Capture II Assay (HC), the Roche Linear Array HPV Genotyping Assay (LA) and the Kurabo GeneSquare Microarray (GS). The main goals of the study were to correlate cytology with HPV detection and to determine agreement between assay pairs for HPV detection. Thin-prep Pap smears were performed and supernates were tested by HC, LA, and GS. For specimens reacting with the HPV 52/33/35/58 probe in the LA assay, type-specific PCR was performed for HPV types 52, 33, 35, or 58. Binomial proportions and kappa coefficients were calculated for agreement between assays. Cytology results and supernatant were available for 202 subjects. HPV detection increased with worsening cytologic abnormality in all three assays. For all cytologic groups, LA and GS detected more HPV (all and oncogenic) than HC. However, for detection of oncogenic HPV types represented in all three assays, differences between assays were less pronounced. The highest agreement was between LA and GS. In four of 12 specimens reacting with the HPV 52/33/35/58 probe in the LA assay but deemed HPV 52-LA-negative using an algorithm provided by the manufacturer, the presence of HPV 52 was confirmed using type-specific HPV 52 PCR. All four of these specimens were also GS-positive for HPV 52.

WITHDRAWN: Risedronate for the prevention and treatment of postmenopausal osteoporosis.

BACKGROUND: Postmenopausal osteoporosis results in an increased susceptibility to low-trauma fractures due to reduced bone volume and microarchitectural deterioration. Risedronate, a third generation bisphosphonate, has been shown in multiple clinical trials to reduce fracture risk and improve bone mineral density in postmenopausal women with osteoporosis. First and second generation bisphosphonates are known to have gastrointestinal side-effects and risedronate may be better tolerated. OBJECTIVES: To systematically review the efficacy of risedronate on bone density, and fracture reduction in postmenopausal women. SEARCH STRATEGY: The Cochrane Controlled Trials Registry Medline, and Current Contents were searched from 1990 - 2001. The electronic search was supplemented by handsearching four osteoporosis journals and their conference proceedings, as well as contacting content experts and industry sources for unpublished data. SELECTION CRITERIA: We included eight trials that randomised women to risedronate or an alternative (placebo or calcium and /or vitamin D) and measured bone mineral density for at least one year. DATA COLLECTION AND ANALYSIS: For each trial three independent reviewers assessed the methodological quality and abstracted data. Data was extracted for outcomes of fracture, bone mineral density and adverse events. The more conservative random effects model was used to pool data. The quality of trials was assessed according to the Jadad five-point scale. MAIN RESULTS: Both vertebral and non-vertebral fractures were statistically and clinically reduced with risedronate. Eleven out of one hundred women who received risedronate had a vertebral fracture compared to 17 out of one hundred of those who received calcium and vitamin D (pooled relative risk for vertebral fractures of 0.64 (95% CI 0.52 - 0.77). Three percent of participants who received risedronate had a non-vertebral fracture compared to 4.6% of those who received calcium and vitamin D (pooled relative risk for nonvertebral fractures of 0.73 (95% CI 0.61 - 0.87). The weighted mean difference for the percent change from baseline for bone mineral density with 5 mg daily for lumbar spine, femoral neck and trochanter was 4.54% (95%CI 4.12 - 4.97), p<0.01; 2.75% (95% CI 2.32 - 3.17), p<0.01; and 4.38% (95% CI 3.51 - 5.25), p<0.01 respectively. AUTHORS' CONCLUSIONS: There is good evidence for the efficacy of risedronate in the reduction of both vertebral and non-vertebral fractures. In addition, there is evidence from randomized trials that risedronate is able to achieve this without increasing risk for overall withdrawals due to adverse effects.

Risedronate for the prevention and treatment of postmenopausal osteoporosis.

BACKGROUND: Postmenopausal osteoporosis results in an increased susceptibility to low-trauma fractures due to reduced bone volume and microarchitectural deterioration. Risedronate, a third generation bisphosphonate, has been shown in multiple clinical trials to reduce fracture risk and improve bone mineral density in postmenopausal women with osteoporosis. First and second generation bisphosphonates are known to have gastrointestinal side-effects and risedronate may be better tolerated. OBJECTIVES: To systematically review the efficacy of risedronate on bone density, and fracture reduction in postmenopausal women. SEARCH STRATEGY: The Cochrane Controlled Trials Registry Medline, and Current Contents were searched from 1990 - 2001. The electronic search was supplemented by handsearching four osteoporosis journals and their conference proceedings, as well as contacting content experts and industry sources for unpublished data. SELECTION CRITERIA: We included eight trials that randomised women to risedronate or an alternative (placebo or calcium and /or vitamin D) and measured bone mineral density for at least one year. DATA COLLECTION AND ANALYSIS: For each trial three independent reviewers assessed the methodological quality and abstracted data. Data was extracted for outcomes of fracture, bone mineral density and adverse events. The more conservative random effects model was used to pool data. The quality of trials was assessed according to the Jadad five-point scale. MAIN RESULTS: Both vertebral and non-vertebral fractures were statistically and clinically reduced with risedronate. Eleven out of one hundred women who received risedronate had a vertebral fracture compared to 17 out of one hundred of those who received an alternative treatment (pooled relative risk for vertebral fractures of 0.64 (95% CI 0.52 - 0.77). Three percent of participants who received risedronate had a non-vertebral fracture compared to 4.6% of those who received an alternative treatment (pooled relative risk for nonvertebral fractures of 0.73 (95% CI 0.61 - 0.87). The weighted mean difference for the percent change from baseline for bone mineral density with 5 mg daily for lumbar spine, femoral neck and trochanter was 4.54% (95%CI 4.12 - 4.97), p<0.01; 2.75% (95% CI 2.32 - 3.17), p<0.01; and 4.38% (95% CI 3.51 - 5.25), p<0.01 respectively. REVIEWER'S CONCLUSIONS: There is good evidence for the efficacy of risedronate in the reduction of both vertebral and non-vertebral fractures. In addition, there is evidence from randomized trials that risedronate is able to achieve this without increasing risk for overall withdrawals due to adverse effects.

Inhibitory mechanisms in autism spectrum disorders: typical selective inhibition of location versus facilitated perceptual processing.

BACKGROUND: This study examined the inhibitory control mechanisms of selective attention in autism spectrum disorders. Two issues were engaged: First, we extend previous findings of normal inhibition of distractor identity in autism by examining whether inhibition of spatial location is also spared. The second issue concerns the selectivity of inhibition. In non-clinical participants inhibition is selectively directed to the properties of the distractor that compete for the control of action; we examined whether individuals with autism also show normal selectivity of inhibition. METHOD: A negative priming task was used to examine selective spatial inhibition in participants with autism relative to matched non-clinical controls. RESULTS: We discovered that inhibition of distractor spatial location is within normal limits in autism, as is the ability to selectively direct inhibition to task-relevant stimulus features. In addition, we unexpectedly found that the irrelevant perceptual feature of colour produced a facilitation effect in autism, which has not been observed previously in typical controls. CONCLUSIONS: Evidence of colour facilitation implicates more fluent, but presumably less adaptive, perceptual processes in autism.

Clinical estimation of trunk position among mechanically ventilated patients.

OBJECTIVES: Trunk position at 45 degrees from the horizontal is associated with a decreased risk of gastroesophageal aspiration. The objectives of this study were to determine the accuracy of trunk flexion estimates compared to a reference standard measurement, and to determine agreement about trunk flexion among ICU clinicians. DESIGN: Prospective observational study. SETTING: Two university-affiliated medical-surgical ICUs. PATIENTS AND PARTICIPANTS: Thirty-three mechanically ventilated ICU patients, seven residents, two fellows, three intensivists, and twenty-eight bedside nurses. INTERVENTIONS: Prospectively, concurrently, and independently during rounds, one bedside nurse, one resident, one fellow, and one intensivist clinically estimated the trunk flexion of mechanically ventilated patients. To record the reference standard, a trained investigator measured trunk position in the vertical plane using a goniometer. MEASUREMENTS AND RESULTS: We made 438 clinical assessments on 33 patients aged 57.2+/-19.4 (SD) years with an APACHE II score of 27.3+/-9.4. Mean trunk flexion estimates were: nurses 24.3+/-12.3 degrees from the horizontal, residents 20.2+/-13.7, fellows 20.3+/-10.8, and intensivists 21.1+/-13.1 compared to the reference standard measurement 16.2+/-9.0 degrees. The accuracy of trunk flexion estimates was fair to moderate [intraclass correlation for reference standard versus nurses (ICC 0.42), residents (ICC 0.52), fellows (ICC 0.36), and intensivists (ICC 0.55)]. The agreement among different groups of clinicians was moderate. CONCLUSIONS: In mechanically ventilated patients, we found that clinical estimates of trunk position were moderately good, agreement amongst caregivers was moderately good, but that all clinicians tended to overestimate the angle of semirecumbency.

Cardiopulmonary resuscitation directives on admission to intensive-care unit: an international observational study.

BACKGROUND: Resuscitation directives should be a sign of patient's preference. Our objective was to ascertain prevalence, predictors, and procurement pattern of cardiopulmonary resuscitation directives within 24 h of admission to the intensive-care unit (ICU). METHODS: We enrolled 2916 patients aged 18 years and older from 15 ICUs in four countries, and recorded whether, when, and by whom their cardiopulmonary resuscitation directives were established. By polychotomous logistic regression we identified factors associated with a resuscitate or do-not-resuscitate directive. FINDINGS: Of 2916 patients, 318 (11%; 95% CI 9.8-12.1) had an explicit resuscitation directive. In 159 (50%; 44.4-55.6) patients, the directive was do-not-resuscitate. Directives were established by residents for 145 (46%; 40.0-51.3) patients. Age strongly predicted do-not-resuscitate directives: for 50-64, 65-74, and 75 years and older, odds ratios were 3.4 (95% CI 1.6-7.3), 4.4 (2.2-9.2), and 8.8 (4.4-17.8), respectively. APACHE II scores greater than 20 predicted resuscitate and do-not-resuscitate directives in a similar way. An explicit directive was likely for patients admitted at night (odds ratio 1.4 [1.0-1.9] and 1.6 [1.2-2.3] for resuscitate and do-not-resuscitate, respectively) and during weekends (1.9 [1.3-2.7] and 2.2 [1.5-3.2], respectively). Inability to make a decision raised the likelihood of a do-not-resuscitate (3.7 [2.6-5.4]) than a resuscitate (1.7 [1.2-2.3]) directive (p=0.0005). Within Canada and the USA, cities differed strikingly, as did centres within cities. INTERPRETATION: Cardiopulmonary resuscitation directives established within 24 h of admission to ICU are uncommon. As well as clinical factors, timing and location of admission might determine rate and nature of resuscitation directives.

Changes in physical functioning in institutionalized older adults.

PURPOSE: Chronic care and long-term care facilities have a responsibility to provide care that enables residents to attain or maintain their maximal functional capacity. This paper uses the Minimum Data Set (MDS) to examine changes in functional health. METHODS: One hundred and thirty-eight residents were assessed quarterly using the MDS over a 12 month period in a chronic care and long-term care institution. Physical functioning was conceptualized in two areas of physical limitations (e.g. bed mobility) and disability (e.g. dressing). RESULTS: Ten percent of the residents physical functioning improved. Gender, range of motion score at baseline, change in bed mobility and change in short term memory were strong independent predictors of changes in functional activity FL adjusted R2 = 0.23, F(5156) = 10.47, p<0.0001. The strongest independent predictors of change in ADL were gender, balance while standing at baseline, joint range of motion at baseline and change in depression scores, and weight loss, adjusted R2 = 0.24 , F(4157)= 13.38, p < 0.0001. CONCLUSIONS: Most residents' physical functioning showed a deterioration or remained stable. Impairments which best explained changes in functioning such as range of motion or balance in standing are modifiable and should be targeted in interventions by nursing and rehabilitation staff.

Bacteremia in hospitalized patients with human immunodeficiency virus: A prospective, cohort study.

BACKGROUND: Bacterial infections complicate the course of patients with human immunodeficiency virus infection. The purpose of this study was to describe the bacterial pathogens causing blood stream infection, identify the risk factors for the development of blood stream infection and determine the impact of blood stream infection on the outcome of patients infected with human immunodeficiency virus. METHODS: The incidence, etiology, risk factors and outcome of bacterial blood stream infection were prospectively determined in 1,225 consecutive hospitalizations of adults with human immunodeficiency virus infection. RESULTS: Blood stream infection occurred in 88 hospitalizations (7%); 73 of 89 infections (82%) were community acquired. The most commonly isolated gram-positive organism was Streptococcus pneumoniae (21); gram-negative, Escherichia coli (14). Blood stream infection was detected in 8% of African Americans and 22% of Hispanics compared with 2% of whites (P = 0.0013). Patients with blood stream infection had higher white blood cell counts (median, 6.5 vs. 4.9 x 109/L; P = 0.0002) and mortality (18% vs. 4%; P < 0.0001) than patients without infection. CONCLUSIONS: In patients with human immunodeficiency virus, blood stream infection is associated with an increased mortality rate. Recognition of the incidence, etiology, and risk factors of blood stream infection in patients with human immunodeficiency virus infection could lead to measures that reduce the increased mortality.

On the strategic modulation of the time course of facilitation and inhibition of return.

In studies of exogenous attentional orienting, response times for targets at previously cued locations are often longer than those for targets at previously uncued locations. This effect is known widely as inhibition of return (IOR). There has been debate as to whether IOR can be observed in discrimination as well as detection tasks. The experiments reported here confirm that IOR can be observed when target discrimination is required and that the cue-target interval at which IOR is observed is often longer in discrimination than in detection tasks. The results also demonstrate that the later emergence of IOR is related to perceptual discrimination rather than to response selection differences between discrimination and detection tasks. More difficult discrimination tasks lengthen the SOA at which IOR emerges. In contrast, increasing task difficulty by adding a distractor to the location opposite the target shortens the SOA at which IOR emerges. Together, the results reveal an adaptive interaction between exogenous and endogenous attentional systems, in which the action of the orienting (exogenous) system is modulated endogenously in accord with task demands.

Tissue/blood and tissue/water partition coefficients for propofol in sheep.

The primary objective of this study was to determine in vivo tissue/blood partition coefficients of propofol for use in physiological modelling of its pharmacokinetics. The sheep was used as an animal model. In the main series of experiments, crossbred ewes received a bolus of propofol 1% (Diprivan) followed by an infusion during which blood concentrations were measured at intervals. After 2 h, the sheep were killed with an injection of potassium chloride, and tissue samples were taken for storage at -20 degrees C and subsequent analysis. Tissue/blood partition coefficients depend on the amount of triglyceride which accumulates in blood from the propofol vehicle; for blood, free of added triglyceride, the following coefficients were calculated: brain, 3.23; heart, 5.94; kidney, 2.46; spleen, 1.86; semimembranosus muscle, > or = 1.61; triceps muscle, > or = 1.47. Calculated tissue/water coefficients were 35 times greater. There was indirect evidence of extraction of propofol by the lungs.

Development and testing of formal protocols for oxygen prescribing.

The absence of standardized assessment protocols with well- defined measurement properties limits comparison of outcomes among those receiving long-term oxygen therapy (LTOT). We describe simple protocols for a hospital test, a simulated home test, and an actual home test, their reliability and relationship to each other. Stable patients with exercise hypoxemia participated. In 74 patients who completed four exercise tests, correlations between tests ranged from 0.85 to 0.78. Of these 27.0% had the same prescription from all four tests. In 46% prescriptions were within 1 L/ min and in 27% within 2 L/min. During exercise the hospital tests suggested slightly higher oxygen prescriptions than did the simulated home tests (2.5 L/min versus 2.0 L/min, p < 0.001). In 23 patients who participated in actual home assessments, the correlations between the home test, the hospital, and the simulated home tests were 0.22 (95% CI -0.24 to 0.67) and 0.27 (95% CI -0.18 to 0.72). In conclusion, standardizing tests for the assessment of LTOT is important. We describe simple hospital and simulated home tests that are reproducible, easy to carry out, and correlate well with each other.

Comparison of trochlear block recession and trochlear wedge recession for canine patellar luxation using a cadaver model.

OBJECTIVE: To compare trochlear block recession (TBR) to trochlear wedge recession (TWR) with regards to patellar depth (percentage of patellar volume under the trochlear ridges), patellar articular contact, percentage of recessed trochlear surface area, and resistance to patellar luxation. STUDY DESIGN: In vitro computed tomography (CT) and biomechanical evaluation using a cadaver model. SAMPLE POPULATION: Twelve normal, large-breed canine cadavers. METHODS: Bilateral pelvic limb specimens with intact stifle joints were mounted on a positioning device. The femoral trochlear ridges were reduced to provide a standard shallow trochlea. TBR or TWR was performed to a standard depth randomly on paired specimens. CT and biomechanical evaluations were performed pre- and postoperatively in both an extended (148 degrees ) and flexed (113 degrees ) stifle position. CT images were digitized and measurements made using an image-analysis software program. Biomechanical testing consisted of applying 40 degrees of internal tibial rotation and documenting patellar luxation. RESULTS: The change in trochlear depth (depth of recession) was not significantly different between groups. In the extended stifle position (patella in the proximal trochlea), patellar depth and patellar articular contact with the recessed trochlea were significantly greater after TBR compared with TWR. The percentage of recessed trochlear surface area was significantly greater after TBR compared with TWR. In the extended position, a smaller percentage of the patellae luxated within 40 degrees of internal tibial rotation after TBR compared with TWR. CONCLUSIONS: TBR increases proximal patellar depth, increases patellar articular contact with the recessed proximal trochlea, recesses a larger percentage of trochlear surface area, and results in a greater resistance to patellar luxation in an extended position as compared with TWR. CLINICAL RELEVANCE: TBR may help limit the development of stifle DJD in dogs treated for canine patellar luxation.